This invention relates to the field of optical indicia readers, and more particularly to bar code readers.
Electro-optical readers, such as bar code symbol readers, are now quite common. Typically, a bar code symbol comprises one or more rows of light and dark regions, typically in the form of rectangles. The widths of the dark regions, i.e., the bars, and/or the widths of the light regions, i.e., the spaces, between the bars indicate encoded information to be read.
A bar code symbol reader illuminates the symbol and senses light reflected from the coded regions to detect the widths and spacings of the coded regions and derive the encoded information. Bar code reading type data input systems improve the efficiency and accuracy of data input for a wide variety of applications. The ease of data input in such systems facilitates more frequent and detailed data input, for example to provide efficient inventories, tracking of work in progress, etc. To achieve these advantages, however, users or employees must be willing to consistently use the readers. The readers therefore must be easy and convenient to operate.
A variety of bar code readers are known. One type of reader is an optical scanner which scans a beam of light, such as a laser beam, across the symbols. Laser scanner systems and components of the type exemplified by U.S. Pat. Nos. 4,387,297 and 4,760,248xe2x80x94which are owned by the assignee of the instant invention and are incorporated by reference hereinxe2x80x94have generally been designed to read indicia having parts of different light reflectivity, i.e., bar code symbols, particularly of the Universal Product Code (UPC) type, at a certain working range or reading distance from a hand-held or stationary scanner. The reader disclosed in the above-listed patents includes a scanning element for moving the laser beam across a bar code symbol. A user aims the reader at a bar code symbol from a position in which the reader is spaced from the symbol, i.e., not touching the symbol or moving across the symbol.
In other scanners where there are no scanning elements, the user must physically move (xe2x80x9cswipexe2x80x9d) the reader, and the illumination beam, across the bar code. The prior art bar code readers that require physical swiping across bar codes are called xe2x80x9cwandxe2x80x9d readers. This type of scanning has been done with wand or pen-shaped scanners that are held in the fingers like a writing pen. This type of scanning leads to poor scanning performance because inexperienced users sometimes hold the pen scanner, or a wand, either too perpendicular to the symbol or too tilted, both of which cause reading failures. Wand readers typically use light emitting diodes (LEDs) to illuminate a bar code. To scan the bar code, the user positions the wand reader over the bar code and operates a trigger switch to activate the light source and a signal processing circuitry. Once the light source has been activated, the user swipes the reader over the bar code and the processing circuitry processes the returned signal.
As stated above, these pen-shaped scanners generally use light emitting diodes (LEDs) as a light source and a photodetector (which could be a photo transistor, photodiode or another light detecting component or device) that have their electrical leads soldered to the end of a long narrow circuit board within the pen housing. The bodies of the LED and photodetector are positioned by a support structure in the proper locations as required by the optical system design. Generally, this involves some manual assembly, hand soldering, and in many cases manual alignment. Glue is often used to assure that all components remain in their proper positions throughout the life of the product. These manual operations and adjustments add costs in manufacturing of the pen-shaped scanners and translate into a higher price paid for these bar-code readers by the consumers.
A need for an extremely inexpensive and reliable bar code symbol reader exists for various cost-sensitive scanning applications. These include home shopping by scanning bar codes in printed catalogs, retrieving via the Internet information related to advertised products by scanning bar codes in printed advertisements, programming of electronic games, toys, and appliances, etc.
Generally bar code symbol readers known in the art are too expensive for these applications. Therefore, there is a need for a bar code reader for the use in these applications that does not utilize costly lenses, mirrors, light pipes, optical fibers, optical filters, and other optical components generally found in the bar-code readers currently known in the art.
Another limitation of the bar code symbol readers known in the art, particularly the contact wand bar code scanners, is that they have very limited depth of focus. This is particularly a problem when scanning over a curved surface. The LED illuminates the same part of the symbol that is visible to a photodetector. When the aperture is lifted off the surface, as often happens with curved surfaces, the photodiode can no longer see the area of the symbol that is illuminated, resulting in a scan failure. Therefore, there is a need for a bar code reader with longer depth of field and depth of focus, that is able to scan over the curved surfaces and/or through the thick plastic protective packaging that is used with CDs and other products.
Another shortcoming of the bar code symbol readers known in the art, particularly with contact wand bar code scanners, is that when the stray light (light that is not reflected off a bar code) reaches the photodetector in a reader, it causes a fixed current to be produced by the detector, which adds to the varying current produced by scanning a bar code. This translates to an offset voltage at the output of the current-to-voltage converter. This offset typically varies from unit to unit, and is usually adjusted out or compensated for with a variable resistor that must be adjusted on each individual unit that is built. This manual adjustment process is expensive and undesirable in a low-cost scanner.
One objective of the present invention is to provide a bar code symbol reader that is inexpensive in production and suitable for home shopping by scanning bar codes in printed catalogs, retrieving via the Internet information related to advertised products by scanning bar codes in printed advertisements, programming of electronic games, toys, and appliances, and other similar applications.
Another objective of the present invention is to provide a low cost bar code symbol reader that eliminates the need for optical components, optical alignment, hand soldering, or gluing of the LED or photodetector.
A further objective of the present invention is to provide a low cost bar code symbol reader that would eliminate read failures due to improper scanner angle with respect to the symbol and improve performance of a scanner when scanning over curved surfaces by extending the depth of focus and depth of field of the scanner with reading aperture that is elongated in a direction perpendicular to the direction the scanner is moved across the symbol.
Another objective of the scanner according to the present invention is to provide a simple design, where the whole tip of the scanner may be replaced, allowing for quick and easy installation and maintenance of the scanner. Additionally, the replaceable tip may come in various sizes and allow the scanner to be adjusted or optimized for scanning of symbols of various different kinds and sizes.
Yet another objective of the present invention is to provide an inexpensive reader (or scanner) that could be incorporated into the same housing as the car alarm control, a remote garage door opener, TV remote controls, portable telephones, personal digital assistants, palm top computers, programmable calculators, pagers, etc.
Another use for the simple reader of the present invention is in improved card readers (commonly called swipe readers), which would allow to read two or more bar codes printed on one card with a single swipe, and to improve the first pass read rate when swiping cards that have damaged symbols.
Another objective is to provide a simple and inexpensive reader that could be used to sense other kinds of markings, such as pencil marks on lottery tickets, school tests, and postal codes.